Smoking article with mouth end cavity

ABSTRACT

A smoking article (10) comprises a tobacco rod (12) and a filter (14) connected to the tobacco rod (12). The filter (14) comprises a first filter segment (18, 20) comprising one or more breakable capsules, wherein each breakable capsule comprises an outer shell and an inner core containing an additive. The filter (14) further comprises a hollow tube segment (22) downstream of the first filter segment (18, 20) and positioned between a downstream end of the first filter segment (18, 20) and the mouth end of the filter (14). The hollow tube segment (22) defines a cavity (24) at the mouth end of the filter (14). A plug wrap (23) circumscribes the first filter segment (18, 20) and the hollow tube segment (22), wherein the plug wrap (23) has a basis weight of less than 90 grams per square metre.

The present invention relates to a smoking article having a mouth endcavity defined by a hollow tube segment.

Filter cigarettes typically comprise a cylindrical rod of tobacco cutfiller surrounded by a paper wrapper and a cylindrical filter axiallyaligned in an abutting end-to-end relationship with the wrapped tobaccorod. The cylindrical filter typically comprises a filtration materialcircumscribed by a paper plug wrap. Conventionally, the wrapped tobaccorod and the filter are joined by a band of tipping wrapper, normallyformed of an opaque paper material that circumscribes the entire lengthof the filter and an adjacent portion of the wrapped tobacco rod.

A number of smoking articles in which tobacco is heated rather thancombusted have also been proposed in the art. In heated smokingarticles, an aerosol is generated by heating a flavour generatingsubstrate, such as tobacco. Known heated smoking articles include, forexample, electrically heated smoking articles and smoking articles inwhich an aerosol is generated by the transfer of heat from a combustiblefuel element or heat source to a physically separate aerosol formingmaterial. During smoking, volatile compounds are released from theaerosol forming substrate by heat transfer from the fuel element andentrained in air drawn through the smoking article. As the releasedcompounds cool they condense to form an aerosol that is inhaled by theconsumer. Smoking articles in which a nicotine-containing aerosol isgenerated from a tobacco material, tobacco extract or other nicotinesource, without combustion or heating, are also known.

Sometimes it is desirable to provide the filter section of a smokingarticle with a cavity at the mouth end. However, such mouth end cavitiesare prone to collapse or deformation during manufacture of the smokingarticle and during subsequent handling by the consumer, particularlywhen the filtration material includes one or more breakable flavourcontaining capsules which must be ruptured by squeezing the filter priorto smoking.

It would therefore be desirable to provide a smoking article having amouth end cavity which is resistant to collapse.

According to a first aspect, the present invention provides a smokingarticle comprising a tobacco rod and a filter connected to the tobaccorod. The filter comprises a first filter segment comprising one or morebreakable capsules, wherein each breakable capsule comprises an outershell and an inner core containing an additive. The filter furthercomprises a hollow tube segment downstream of the first filter segment,the tube segment positioned between a downstream end of the first filtersegment and the mouth end of the filter. The hollow tube segment definesa cavity at the mouth end of the filter. A plug wrap circumscribes thefirst filter segment and the hollow tube segment, wherein the plug wraphas a basis weight of less than 90 grams per square metre.

In some embodiments, the hollow tube segment extends from the downstreamend of the first filter segment to the mouth end edge of the filter.

As used herein, the terms “upstream” and “downstream” are used todescribe the relative positions of elements, or portions of elements, ofthe smoking article in relation to the direction in which a user drawson the smoking article during use thereof. Smoking articles as describedherein comprise a downstream end and an opposed upstream end. In use, auser draws on the downstream end of the smoking article. The downstreamend, which is also described as the mouth end, is downstream of theupstream end, which may also be described as the distal end.

By forming a mouth end cavity with a hollow tube segment, the presentinvention advantageously provides a smoking article having a mouth endcavity with improved resistance to collapse or deformation. Suchresistance to collapse or deformation can advantageously eliminate theneed to use stiff, high basis weight plug wraps and tipping wrapperswhich might otherwise be required to prevent collapse of the mouth endcavity. Such high basis weight plug wraps and tipping wrappers areundesirable since they can become creased or folded during manufactureof the smoking article, and they can also add other costly steps to themanufacturing process such as the need for online laser perforationventilation. Furthermore, high basis weight plug wraps and tippingwrappers can make it difficult for a consumer to deform the filter inorder to break the one or more capsules contained therein. Byeliminating the need for such high basis weight plug wraps and tippingwrappers and by forming the mouth end cavity using a hollow tubesegment, smoking articles in accordance with the present invention allowa consumer to easily deform the filter at the first filter segment inorder to break the one or more capsules contained therein, whilstensuring the mouth end cavity is sufficiently resistant to deformationor collapse.

Since smoking article filters are generally circular in cross section,the resistance of the hollow tube segment to collapse or deformation maybe such that the ovality of the hollow tube segment after a 50%deformation of the filter is less than 25%, preferably less than about20%. In this case, the mouth end cavity of the smoking articles willretain or resume a generally circular cross section, even after a 50%deformation of the filter. The particular test procedure for conductingdeformations of the filter in accordance with present invention isdescribed in detail below.

The term “ovality” as used herein means the degree of deviation from aperfect circle. Ovality is expressed as a percentage and themathematical definition is given below.

To determine the ovality of a segment of a smoking article (such as ahollow tube segment) in accordance with the present invention, the mouthend is viewed along the longitudinal direction of the smoking article.For example, the smoking article can be positioned on its mouth end on atransparent stage so that an image of the mouth end of the article isrecorded by a suitable imaging device located below the stage. Dimension“a” is taken to be the largest external diameter of the segment at itsdownstream end and dimension “b” is taken to be the smallest externaldiameter of the segment at its downstream end. The process is repeatedfor a total of ten smoking articles having the same design and thenumber average of the ten ovality measurements is recorded as theovality for that design of smoking article.

As described above, the resistance of the hollow tube segment tocollapse or deformation may be such that the ovality of the hollow tubesegment after a 50% deformation of the filter is less than 25%,preferably less than about 20%. This is itself a novel and inventivearrangement, and so according to a second aspect the present inventionprovides a smoking article comprising a tobacco rod and a filterconnected to the tobacco rod. The filter comprises a first filtersegment and a hollow tube segment downstream of the first filtersegment, the tube segment positioned between a downstream end of thefirst filter segment and the mouth end of the filter. The ovality of thehollow tube segment after a 50% deformation of the filter is less than25%, preferably less than about 20%.

In some embodiments, the hollow tube segment extends from the downstreamend of the first filter segment to the mouth end edge of the filter.

The resistance of the hollow tube segment to collapse or deformation mayalso be such that the ovality of the tube segment after a 67%deformation of the filter is preferably less than about 35%, morepreferably less than about 30%, for smoking articles in accordance withboth aspects of the present invention. Additionally, or alternatively,the resistance of the hollow tube segment to collapse or deformation maybe such that the difference between the ovality of the tube segmentafter 50% deformation of the filter and the ovality of the tube segmentprior to deformation is less than about 25%, preferably less than about20%. For example, where the ovality of the tube segment prior todeformation is 5%, the ovality of the tube segment after a 50%deformation of the filter is preferably less than 30%, more preferablyless than 25%.

In some embodiments, the ovality of the hollow tube segment after a 50%deformation of the filter performed after the smoking article has beensubjected to a smoking test is preferably less than about 35%, morepreferably less than about 30%. Alternatively, or in addition, theovality of the tube segment after a 67% deformation of the filterperformed after the smoking article has been subjected to a smoking testis preferably less than about 45%, more preferably less than about 40%.This advantageously provides consistency in the ovality of the mouth endcavity during smoking of smoking articles in accordance with bothaspects of the present invention.

The smoking test used for testing smoking articles in accordance withboth aspects of the present invention is described in detail below.Where it is necessary to measure the ovality after deformation testsperformed both before and after smoking, two samples of smoking articleshaving the same design should be used. That is, a non-deformed un-smokedsmoking article should be used for the pre-smoking deformation test, andnon-deformed articles having the same design are subjected to thesmoking test and used for the post-smoking deformation test.

In some embodiments of the invention according to both aspects, thehollow tube segment may be formed from a polymeric material or a papermaterial. For example, the hollow tube segment can be formed from anextruded plastic tube. Preferably, the hollow tube segment is formedfrom a plurality of overlapping paper layers, such as a plurality ofparallel wound paper layers or a plurality of spirally wound paperlayers. Forming the hollow tube segment from a plurality of overlappingpaper layers can help to further improve resistance to collapse ordeformation. Preferably each hollow tube segment comprises at least twopaper layers. Alternatively, or additionally, each hollow tube segmentpreferably comprises fewer than eleven paper layers.

An exemplary method for forming a tube segment from a plurality of woundpaper layers comprises wrapping a plurality of substantially continuouspaper strips in an overlapping manner about a cylindrical mandrel. Thestrips are wrapped in a parallel manner or a spiral manner so as to forma substantially continuous tube on the mandrel. The formed tube may beturned about the mandrel, for example using a rubber belt, so that thepaper layers are continually drawn and wrapped around the mandrel. Theformed tube can then be cut into the required lengths downstream of themandrel.

One factor that may restrict the ability of the hollow tube segment toretain its ovality during smoking of the smoking article is absorptionof moisture into the tube segment during smoking. Therefore, to inhibitthe transfer of moisture from one paper layer to the next during smokingof the smoking article, adjacent paper layers of each tubular member arepreferably adhered together by an intermediate layer of adhesive, whichprovides a barrier to the transfer of moisture between layers.Additionally, or alternatively, the hollow tube segment may comprise acoating layer on an inner surface thereof, which can inhibit absorptionof moisture into the hollow tube segment. In those embodiments in whichthe hollow tube segment is formed from a plurality of paper layers, acoating layer may additionally or alternatively be provided between someor all of the adjacent paper layers. Suitable coating materials include,but are not limited to, waxes, polymeric materials and combinationsthereof. Particularly suitable waxes include vegetable waxes, and otherparticularly suitable materials are ethylcellulose and nitrocellulose.

To increase the resistance of the hollow tube segment to crushing, thefilter preferably has an un-smoked compressive strength of at leastabout 20 Newtons at 50% compression. Alternatively, or in addition, theun-smoked compressive strength of the filter at 50% compression ispreferably less than about 50 Newtons. The term “compressive strength”is a measure of the force required to provide a particular compressionof the filter section of the smoking article. Compressive strength ismeasured using the compressive strength test described in detail below,where the compressive strength of a given smoking article design is thenumber average of the compressive strength measurements for a sample often smoking articles having the same design.

To assist in providing the required resiliency and resistance todeformation or crushing, the hollow tube segment preferably has a wallthickness of at least about 100 micrometres, more preferably at leastabout 150 micrometres. Alternatively, or in addition, the wall thicknessis preferably less than about 500 micrometres, more preferably less thanabout 350 micrometres, most preferably less than about 250 micrometres.

The hollow tube segment preferably extends at least about 2 mm from thedownstream end of the first filter segment in the finished cigarette.This not only provides a mouth end cavity of an appropriate size, butalso ensures sufficient overlap between the hollow tube segment and anywrapper which may circumscribe the tube segment to maintain it in axialalignment with the filter segment. Such wrappers include plug wraps andtipping wrappers. Additionally, or alternatively, the hollow tubesegment preferably extends no more than about 15 mm from the downstreamend of the first filter segment.

In some embodiments of the invention according to the second aspect, itmay be desirable to provide the filter with means for releasing aflavourant or other additive on demand, usually via manual release bythe consumer immediately prior to smoking the article. Therefore, thefilter may comprise at least one filter segment including a flavourantcontaining material, such as one or more breakable capsules comprisingan outer shell and an inner core containing an additive. Preferably theat least one filter segment comprises one or more breakable capsulesdispersed within a fibrous filtration material. The at least one filtersegment may be the first filter segment, or an additional filter segmentwhich may be incorporated into the filter, or a combination thereof.

Similarly, the additive contained within the one or more breakablecapsules of smoking articles in accordance with the first aspect of thepresent invention may include a flavourant.

In embodiments comprising a flavourant containing material, inaccordance with both aspect of the present invention, the at least oneflavour containing filter segment is preferably circumscribed by a plugwrap that is substantially impermeable to the flavourant additive. Thisadvantageously inhibits transfer of the additive through the plug wrapto the outside of the smoking article, where it may undesirably comeinto contact with the consumer's fingers and may tarnish the appearanceof the smoking article.

Where the at least one flavour containing filter segment comprises oneor more breakable capsules, the ovality of the tube segment ispreferably less than 35%, more preferably less than 30%, after a capsulecrush test in which a force corresponding to the crush strength of theone or more capsules is applied to the smoking article. The crushstrength of a capsule corresponds to the compressive force required tobreak open the capsule and release the additive contained within thecapsule when the capsule is disposed within the filter segment. Thecapsule crush test is described in detail below.

Where the capsule crush test is performed after the smoking article hasbeen subjected to a smoking test, the ovality of the tube segment ispreferably less than about 45%, more preferably less than about 40%,after the capsule crush test.

As mentioned above, smoking articles according to both aspects of thepresent invention may comprise additional filter segments in combinationwith the first filter segment. For example, in one embodiment, thesmoking article further comprises a rod end segment between the firstfilter segment and the tobacco rod.

The filtration material within each filter segment of the smokingarticle is preferably a plug of fibrous filtration material, such ascellulose acetate tow or paper. A filter plasticiser may be applied tothe fibrous filtration material in a conventional manner, by spraying itonto the separated fibres, preferably before applying any additionalmaterial to the filtration material. Smoking articles according to bothaspects of the present invention may also include a variety of differenttypes of filter segments or combinations of filter segments that wouldbe known to the skilled person, including restrictors and segments thatare used for adjusting the resistance to draw (RTD). Alternatively, orin addition, smoking articles in accordance with both aspects of thepresent invention may include one or more segments containing carbon,preferably a rod end segment containing carbon.

To connect the hollow tube segment to the first filter segment and anyother filter segments which may be present, the smoking article maycomprise a combining plug wrap which circumscribes the various segmentsof the filter. The combining plug wrap may have a basis weight of lessthan about 90 gsm, preferably less than about 60 gsm, more preferablyless than about 40 gsm. The combining plug wrap preferably has a basisweight of more than about 20 gsm.

The smoking article may include a tipping wrapper circumscribing thefilter and at least a portion of the tobacco rod so as to connect thefilter to the tobacco rod. The tipping wrapper may comprise paper havinga basis weight of less than about 70 gsm, preferably less than about 50gsm. The tipping wrapper preferably has a basis weight of more thanabout 20 gsm.

Smoking articles according to both aspects of the present invention maybe filter cigarettes or other smoking articles in which the tobaccomaterial is combusted to form smoke. Alternatively, smoking articlesaccording to both aspects of the present invention may be articles inwhich the tobacco material is heated to form an aerosol, rather thancombusted. In one type of heated smoking article, the tobacco materialis heated by one or more electrical heating elements to produce anaerosol. In another type of heated smoking article, an aerosol isproduced by the transfer of heat from a combustible or chemical heatsource to a physically separate tobacco material, which may be locatedwithin, around or downstream of the heat source. Both aspects of thepresent invention further encompass smoking articles in which anicotine-containing aerosol is generated from a tobacco material withoutcombustion or heating.

The present invention also provides a method of forming smokingarticles, the method comprising a first step of providing a continuousarray of first filter members and tubular members, wherein a tubularmember is provided between each pair of consecutive first filtermembers. The first filter members each comprise one or more breakablecapsules, each breakable capsule comprising an outer shell and an innercore containing an additive The continuous array of first filter membersand tubular members is then wrapped with a continuous sheet of plug wrapto form a wrapped filter array. The plug wrap has a basis weight of lessthan 90 gsm. Next, the wrapped filter array is cut at an intermediateposition along each of the first filter members to provide multiplefilter rods, each filter rod comprising two first filter segments and atubular member positioned between the first filter segments. A tobaccorod is then provided in axial alignment with and adjacent to each firstfilter segment of each filter rod, and the filter rod and a portion ofeach tobacco rod are wrapped in a tipping wrapper. Finally, the tippingwrapper and the filter rod are cut at an intermediate position along thelength of the tubular member to form two smoking articles, each smokingarticle comprising a tobacco rod connected to a filter. Each filtercomprises a first filter segment and a hollow tube segment positionedbetween the adjacent filter segment and the mouth end of the filter, thehollow tube segment defining a cavity at the mouth end of the filter.

Test Procedures Deformation and Compressive Strength Test

The smoking article to be tested is positioned between a flat surfaceand a circular plate opposed to the flat surface, the circular platehaving a diameter of 10 mm. The edge of the circular plate closest tothe mouth end of the smoking article is positioned 8 mm from the mouthend. The filter is then compressed by moving the circular plate towardsthe flat surface at a constant speed of 100 mm per second. The forceapplied by the circular plate is increased until the desired deformationof the portion of the smoking article between the circular plate and theflat surface is achieved. For example, to achieve a 50% deformation, thecompressed portion of the smoking article is compressed to a diameter of50% of the diameter of that portion prior to compression. Similarly, toachieve a 67% deformation, the smoking article is compressed until thecompressed portion is reduced to a diameter of 33% of the diameter ofthat portion prior to compression. The diameter is measured in thedirection of compression, which is the direction extending between theflat surface and the circular plate. Once the desired compression hasbeen achieved, the force required to provide that compression is notedas the compressive strength of the filter. The circular plate is thenretracted so that the compressive force is removed. The smoking articleis left for 30 seconds to expand before any further tests ormeasurements are performed.

Smoking Test

To simulate the smoking of a smoking article, the smoking article issubjected to a standard smoking test under ISO conditions (35 ml puffslasting 2 seconds each, every 60 seconds). In the ISO test method, thesmoking article is smoked with the ventilation zone fully uncovered.

Capsule Crush Test

To perform a capsule crush test in accordance with the presentinvention, a smoking article including a breakable capsule is positionedbetween a lower plate having a diameter of 150 mm and an upper platehaving a diameter of 20 mm. The portion of the smoking article housingthe breakable capsule is positioned between the two plates such that theplates are centred on the location of the capsule. The smoking articleand the capsule are then compressed by moving the upper plate towardsthe lower plate at a constant speed of 30 mm per minute. The forceapplied by the upper plate is increased until the capsule breaks, atwhich point the maximum compressive load applied by the upper plate isrecorded as the crush strength of the capsule. The test is terminatedwhen the maximum compressive load is reached and the upper plate isretracted to remove the compressive force from the smoking article. Thesmoking article is then left for 30 seconds to expand before any furthertests or measurements are performed, such as ovality measurements.

The invention will now be further described, by way of example only,with reference to the accompanying drawings in which:

FIG. 1 shows a smoking article in accordance with the present invention;

FIG. 2 shows the mouth end of the smoking article of FIG. 1 with thefilter unwrapped;

FIG. 3 shows an exemplary method of forming a tubular member for forminghollow tube segments in accordance with the present invention;

FIG. 4 shows a method of forming a plurality of smoking article filterrods for use in producing smoking articles according to the presentinvention;

FIG. 5 shows a dual filter rod;

FIG. 6 shows a quad filter rod; and

FIG. 7 shows an exemplary method for forming a smoking article using adual filter rod.

FIGS. 1 and 2 show a filter cigarette 10 in accordance with the presentinvention. The cigarette 10 comprises a wrapped rod 12 of tobacco cutfiller which is attached at one end to an axially aligned filter 14. Atipping wrapper 16 circumscribes the filter 14 and a portion of thewrapped rod 12 of tobacco to join together the two portions of thecigarette 10.

As shown in FIG. 2, the filter 14 comprises a rod end filter segment 18,a flavour containing filter segment 20, and a mouth end hollow tubesegment 22. The segments 18, 20 and 22 are circumscribed by a combiningplug wrap 23 which connects the three segments to form the filter 14.The combining plug wrap 23 has a basis weight of less than 90 gsm. Oneor more of the segments 18, 20, 22 may also be wrapped in an individualplug wrap.

The rod end filter segment 18 and the flavour containing filter segment20 are formed of a suitable filtration material, such as celluloseacetate tow. Furthermore, the flavour containing filter segment 20comprises a suitable flavourant provided in the form of one or morebreakable capsules contained within the flavour containing filtersegment 20. The one or more breakable capsules may be ruptured by theconsumer when desired by squeezing the flavour containing filter segment20 between the consumer's fingers.

The mouth end hollow tube segment 22 defines a mouth end cavity 24 inthe filter 14 which extends between the downstream end of the flavourcontaining filter segment 20 and the mouth end edge of the filter 14.The mouth end hollow tube segment 22 may be formed of a plurality ofspirally wound paper layers which can further improve the resistance todeformation of the mouth end cavity 24, for example during the ruptureof the one or more breakable capsules when present in the flavourcontaining filter segment 20. The ovality of the tube segment after a50% deformation of the filter 14 is less than 25%.

FIG. 3 shows an exemplary method of forming a tube member 30 which canbe cut to form a plurality of hollow tube segments for use in formingsmoking articles in accordance with the present invention. A pluralityof continuous paper plies 32 are spirally wound around a cylindricalmandrel 34 in a staggered, overlapping arrangement. A suitable adhesivemay be applied to one or more of the plies 32 using an adhesive bath 36prior to winding each ply around the mandrel 34. The plies 32 are drivenby a rubber belt 38 so that the formed tubular member 30 rotates aroundthe mandrel 34 until it is cut into desired lengths further downstream.

To form a plurality of smoking articles in accordance with the presentinvention, the process illustrated in FIGS. 4 to 7 can be used. First, aplurality of filter rods is produced according to the process shown inFIG. 4. A substantially continuous array of filter components is formedby providing a plurality of tubular members 40, a plurality of flavourcontaining filter segments 20 and a plurality of rod end filter members42. A tubular member 40 is provided between each pair of consecutive rodend filter members 42, and a flavour containing filter segment 20 isprovided between each rod end filter member 42 and each tubular member40. The substantially continuous array of filter components is thenwrapped in a continuous sheet of plug wrap 44 to form a wrapped filterarray.

To form a plurality of filter rods, a plurality of first cuts 46 aremade through at least some of the rod end filter members 42 of thewrapped filter array, each first cut 46 positioned at an intermediateposition along the length of the respective rod end filter member 42.The resilience of each tubular member 40 advantageously preventscollapse of the cavities defined therein during the cutting process andsubsequent handling of the filter rods and smoking articlesincorporating filters manufactured from the filter rods.

To form a dual filter rod, as shown in FIG. 5, the wrapped filter arrayis cut through each rod end filter member 42 so as to provide a filterrod having a rod end filter segment 18 at each end, two flavorcontaining filter segments 20 positioned between the two rod end filtersegments 18, and a tubular member 40 positioned between the two flavorcontaining filter segments 20. The dual filter rod essentially definestwo smoking article filters 14 which are joined by a continuous plugwrap 44 and a tubular member 40.

Alternatively, a quad filter rod, as shown in FIG. 6, can be formed bycutting the wrapped filter array through every other filter member 42 soas to provide a filter rod which essentially comprises two joined dualfilter rods.

The formed filter rods can be used to form two or more smoking articles.For example, as shown in FIG. 7, a dual filter rod can be used to formtwo filter cigarettes 10 by placing a tobacco rod 12 in axial alignmentwith each end of the filter rod. A tipping wrapper 50 is then wrappedaround the filter rod and a portion of each tobacco rod 12 adjacent thefilter rod. The tipping wrapper 50, the plug wrap 44 and the tubularmember 40 are then cut along a cut line 52 to form two filtercigarettes. The resilience of the tubular member 40 prevents collapse ordeformation of the mouth end cavities of each cigarette 10 during thecutting process.

To form a plurality of smoking articles using a quad filter rod, thefilter rod is first cut through the rod end filter member 42 to form twodual filter rods. The two dual filter rods can then be used to form foursmoking articles using the method shown in FIG. 7.

1. A smoking article comprising: a tobacco rod; and a filter connectedto the tobacco rod, the filter comprising: a first filter segmentcomprising one or more breakable capsules, each breakable capsulecomprising an outer shell and an inner core containing an additive; ahollow tube segment downstream of the first filter segment and defininga cavity at the mouth end of the filter, the hollow tube segmentpositioned between a downstream end of the first filter segment and themouth end of the filter; and a plug wrap circumscribing the first filtersegment and the hollow tube segment, wherein the plug wrap has a basisweight of less than 90 grams per square metre.
 2. The smoking articleaccording to claim 1, wherein the ovality of the hollow tube segmentafter a 50% deformation of the filter is less than 25%.
 3. The smokingarticle according to claim 1 wherein the ovality of the tube segment isless than 25% after a capsule crush test in which a force correspondingto the crush strength of the one or more capsules is applied to thefirst filter segment.
 4. A smoking article comprising: a tobacco rod;and a filter connected to the tobacco rod, the filter comprising: afirst filter segment; and a hollow tube segment downstream of the firstfilter segment and defining a cavity at the mouth end of the filter, thehollow tube segment positioned between a downstream end of the firstfilter segment and the mouth end of the filter; wherein the ovality ofthe hollow tube segment after a 50% deformation of the filter is lessthan 25%.
 5. The smoking article according to claim 1, wherein thehollow tube segment is formed from a plurality of overlapping paperlayers.
 6. The smoking article according to claim 5, wherein the hollowtube segment is formed from a plurality of spirally wound paper layers.7. The smoking article according to claim 5, wherein adjacent paperlayers of the hollow tube segment are adhered together by anintermediate layer of an adhesive.
 8. The smoking article according toclaim 5, wherein the hollow tube segment comprises at least two paperlayers.
 9. The smoking article according to claim 1, wherein thedifference between the ovality of the tube segment after 50% deformationof the filter and the ovality of the tube segment prior to deformationof the filter is less than 25%.
 10. The smoking article according toclaim 1, wherein the ovality of the hollow tube segment after a 50%deformation of the filter performed after the smoking article has beensubjected to a smoking test is less than 35%.
 11. The smoking articleaccording to claim 1 wherein the hollow tube segment comprises a coatinglayer on an inner surface thereof.
 12. The smoking article according toclaim 1 wherein the compressive strength of the filter is at least 20Newtons at 50% compression.
 13. The smoking article according to claim 1wherein the wall of the hollow tube segment has a thickness of between150 micrometres and 500 micrometres.
 14. The smoking article accordingto claim 1 wherein the hollow tube segment extends at least 2 mm fromthe downstream end of the first filter segment.
 15. The smoking articleaccording to claim 1 further comprising a rod end segment between thefirst filter segment and the tobacco rod.